Everyone thought I was having twins too as my stomach had literally exploded! Im not, theres only one in there! Ive been told the reason I seemed so big, so quick is because as its my second pregnancy, my body knows what to do ths time round and is doing it all quicker.
If it is your booking in appointment with your midwife, all she will do is ask lots of questions about yours and your familys health and ask about your last pregnancy/birth. She will also test your urine sample and probably weigh you, but that is about it. You wont have a clue how many you have in there until your first scan in a few weeks time.
Congratulations though :)